Mean platelet volume has been proposed as a predictor for venous thromboembolism in cancer. We, therefore, investigated the effects of different anti-cancer drugs on mean platelet volume in order to assess its possible value in the risk prediction of a first thromboembolic episode in cancer outpatients during treatment. Pre-treatment mean platelet volumes were retrospectively evaluated in 589 ambulatory patients at the beginning of a new chemotherapy regimen. Moreover, serial changes were evaluated at baseline and before each chemotherapy cycle on 385 of the 589 patients who consented to have additional blood withdrawals during treatment. Cox proportional hazards survival analysis demonstrated a 2.7 hazard ratio (P=0.01) of developing a first venous thromboembolic episode during chemotherapy for patients with baseline mean platelet volumes below the 10(th) percentile (<7.3 fL). This index significantly declined during the first three months of chemotherapy (-6%; P<0.0001) reverting to baseline at the end of treatment. Multivariate regression analysis showed that normal baseline volumes (P=0.012) and platinum-based regimens (P=0.017) were both independent predictors of mean platelet volume decline during chemotherapy which, in turn, was associated with a 2.4 hazard ratio (P=0.044) of venous thromboembolism. In conclusion, low pre-chemotherapy mean platelet volume might be regarded as a predictor of increased venous thromboembolism risk in cancer patients and chemotherapy further decreases platelet volumes, possibly due to drug-induced platelet activation and destruction. Changes in mean platelet volumes during chemotherapy might provide additional information on thromboembolic risk of patients treated with anti-cancer drugs, particularly platinum compounds.
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